Distribution of components in the rare earth ammonia synthesis catalysts and effect of additives

The distribution of components in the HG-1 ammonia catalyst promoted by rare earth oxide (successfully developed by the authors) was analyzed by electron microprobe photography. The results enable us to explain the effect of additives upon the activity as well as the remarkably high lifetime of catalyst.

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HG-1, ( ) , . , .

     

The role of excited states in the photolysis of n-butyraldehyde, II. Intersystem crossing quantum yields

Singlet triplet intersystem crossing quantum yields were determined for n-butyraldehyde, using the photosensitized cis-trans isomerization of piperylene to monitor the process. At room temperature and 313 nm, 0.58±0.05 and 0.72±0.05 were obtained for the triplet yield in the vapor phase and in isooctane, respectively.

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- - - . 0,58±0,05 0,72±0,05 313 .

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For Part I, see Ref. /1/     

Influence of pore diffusion on the rate of n-heptane conversion on a Pt/Al2O3 catalyst under reforming conditions

Under reforming conditions, the rate of n-heptane conversion on a large Pt/Al₂O₃ catalyst grain, in contrast to that in the kinetic region, depends on the hydrogen to hydrocarbon mole ratio. The rate equation for the reaction on a large grain agrees well with the experimental results obtained by a gradientless method under pressure.

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- , , : . , .

     

AlPO4?ZrO2 catalysts, IV. Cyclohexene skeletal isomerization activity of systems obtained in ethylene oxide

The use of AlPO₄–ZrO₂ (weight ratio AlPO₄/ZrO₂=3) as catalyst systems obtained with ethylene oxide and subjected to different stages of heat treatments has been studied through their catalytic activity in the skeletal isomerization of cyclohexene to 1- and 3-methylcyclopentenes (1- and 3MCP). The apparent rate constants and selectivity to 1-MCP are used for an evaluation of the presence and amount of strong acid sites, the only ones capable of giving rise to skeletal isomerization. The decrease in catalytic activity as calcination increases is consistent with not only the decrease in the amount of acid sites measured vs. weaker organic bases but also with the decrease in Brönsted acidity, as shown by the decrease in O–H band intensity.

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AlPO₄–ZrO₂ ( AlPO₄/ZrO₂=3), , 1- 3- (1- 3-). 1- , . , , , O–H.

     

Thermogravimetric and kinetic study of a clodronic acid complex formed with sodium

Thermal stability of the clodronic acid complex formed with sodium (Na₂CCl₂(HPO₃)₂ ·4H₂O) was studied using both dynamic and isothermal thermogravimetric analyses as well as mass spectra. The thermal decomposition has two stages: dehydration and loss of two molecules of hydrogen chloride. Using the isothermal TG data the first step was found to be a phase-boundary reaction while the second step obviously cannot be described with just one reaction mechanism. The final residue of the dynamic TG analyses above 810 K was found to be sodium metaphosphate.

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Zusammenfassung Sowohl mittels dynamischer und thermogravimetrischer Untersuchungen als auch and Hand von Massenspektren wurde die thermische Stabilität des mit Natrium gebildeten Säurekomplexes Na₂CCl₂(HPO₃)₂·4H₂O untersucht. Die thermische Zersetzung vollzieht sich in zwei Schritten: Dehydratation und Verlust von zwei Molekülen HCl. Auf Grund der isothermen TG Angaben ist der erste Schritt eine Phasengrenzreaktion, während der zweite Schritt mit einem einzigen Reaktionsmechanismus nicht eindeutig beschrieben werden kann. Das Endprodukt der DTG Analyse oberhalb 810 K erwies sich als Natriummethaphosphat.

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-Na₂CCl₂/HPO_3/2·4H₂O — , - . , , , . , , . 810 .

     

Study on the thermal behaviours of homo- and copolymers of styrene,MA and AN by thermogravimetry

The thermal behaviours of polystyrene (PS), polymethylacrylate (PMA), polyacrylonitrile (PAN), polystyrene-co-methylacrylate [P(S: MA)](alternate and random), polystyrene-co-acrylonitrile [P(S: AN)] (alternate) and a terpolymer of styrene, methylacrylate and acrylonitrile [P(S: MA: AN)] are discussed on the basis of non-isothermal thermogravimetric studies. The thermal stabilities of the copolymers have been found to be intermediate between of those of the individual homopolymers. The stability of the [P(S: AN)] copolymer is higher than those of the individual homopolymers. The activation energy values are also in accordance with the thermal behaviours of these polymers.

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Zusammenfassung Basierend auf nicht-isotherme thermogravimetrische Untersuchungen wurde das thermische Verhalten von Polystyrol [PS], Polymethacrylat [PMA], Polyacrylnitril [PAN], Polystyrol-co-methacrylat [P(S: MA)] (alternierend und random), Polystyrolco-acrylnitril [P(S: AN)] (alternierend) sowie eines Mischpolymeren von Styrol, Methacrylat und Acrylnitril [P(S: MA: AN)] untersucht. Die thermische Stabilität der Kopolymeren liegt zwischen denen der individuellen Homopolymeren. Die thermische Stabilität des Kopolymeren [P(S: AN)] ist höher als die der individuellen Homopolymeren. Die Werte der Aktivierungsenergie sind ebenfalls in Übereinstimmung mit dem thermischen Verhalten dieser Polymere.

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, , , , ( ), (- ), --. , . - . .

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Presented at the 3rd National Symposium on Thermal Analysis held at VSSC, Trivandrum (India), November, 1981     

Reactivity of allyl (o-halophenyl) ethers with organonickel (0) complexes

The reactivity of allyl (o-halophenyl) ethers with zerovalent nickel complexes, with triphenylphosphine and pyridine as ligands, leading to benzo[b]furan derivatives has been checked. Cyclization products were not isolated, but deallylation, substitution, reduction and rearrangement products were obtained in low to moderate yields. Mechanisms are proposed to explain the formation of these side products.

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-(o-) , , [b] . , , , , . .

     

Ammonia decomposition on polycrystalline Pt at pressures between 1.3 and 93 kPa

The kinetics of ammonia decomposition on polycrystalline Pt at temperatures between 600 and 1700 K and at pressures between 1.3 and 93 kPa were measured and correlated with a Langmuir-Hinshelwood unimolecular reaction rate expression. This rate expression had previously been shown to fit data in the same temperature range for pressures between 2 and 1400 Pa.

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Pt 600–1700 1,3 93 , - . , , , 2 1400 .

     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

Oxidative dehydrodimerization of aromatic hydrocarbons on oxide catalysts

It has been shown that in contrast to benzene, toluene can readily participate in reactions of oxidative coupling. The inertness of benzene is explained by the absence of mobile hydrogen atoms in -position with respect to the unsaturated bond.

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, , . - .

     

Selectivity in cobaloxime catalyzed hydrogenation of nitrobenzene in the presence of olefins. Remarkable effect of isoprene

It has been found that nitrobenzene, in the presence of monoolefins, is effectively hydrogenated with the cobaloxime catalyst. Conjugated dienes and nitrobenzene are both hydrogenated; the extent of hydrogenation of dienes depends upon the structure. A remarkable exception is isoprene, whose presence in the reacting solution completely inhibits the hydrogenation of nitrobenzene. No organometallic compounds of Co(III) have been isolated. Homolytic activation of hydrogen is therefore rather unlikely in this system.

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, . , , , . , . - Co(III). , , - .

     

Isomerization of chemically activated secondary butyl radical

Photolytic decomposition of hydrogen sulfide followed by the addition of energized hydrogen atoms to cisbut-2-ene gives excited sec-butyl radicals. The radicals undergo a 1,3 hydrogen migration as is evidenced by the good agreement between the RRKM calculations and experiment. The contribution of a 1,2 hydrogen shift cannot be excluded. The threshold energies are 153.8 and 176.8 kJ mol^–1 for 1,3 and 1,2 isomerization, respectively.

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-2 .- . 1,3- , . , 1,2- . 153,8 176,8 / 1,3- 1,2-, .

     

Telomerization of butadiene with diethylamine catalyzed by Ni, Pd and Pt allyl halide complexes

The telomerization of butadiene with diethylamine with the formation of the tertiary amine (C₂H₅)₂NC₈H₁₃ is catalyzed by Ni, Pd and Pt allyl halide complexes. Triphenylphosphine increases the activity of such catalysts. The rate of telomerization depends strongly on the [PPh₃]/[M] ratio (M=Pd and Pt) and increases in the series of metals: Ni3H₅PdCl)₂ exceeds that of (-C₃H₅)₂ Pd by more than two orders of magnitude.

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Ni, Pd Pt (C₂H₅)₂NC₈H₁₃. . [PPh₃]/[M], M=Pd Pt, : Ni3H₅PdCl)₂ (-C₃H₅)₂Pd.

     

Temperature programmed desorption (TPD) of carbon monoxide from cobalt surfaces

Three different binding states of CO on cobalt surfaces have been identified by TPD studies. The energetics of these adsorption states and their relevance in Fischer-Tropsch synthesis are considered.

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CO - . -.

     

Trapping adsorption of carbon monoxide located between carbon dioxide adsorbed on magnesium oxide

Carbon monoxide adsorbed on MgO is strongly trapped by the adsorbed carbon dioxide, increasing the heat of adsorption from 85.4 to 184.1 kJ/mol. The trapped CO is thought to be captured by two or three adsorbed CO₂ and becomes less active to react with oxygen.

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, MgO, , 85,4 184,1 /. , CO CO₂ .

     

Isomerization of unsaturated compounds on Pd/Al2O3 in the presence of additives

Studies of the effect of zinc chloride and aluminium additives on the activity of a Pd/Al₂O₃ catalyst (5 wt.%Pd) in the isomerization of heptene-1, allylbenzene,p-allylphenol and 4-allyl-2-methoxyphenol (eugenol) indicate that the rate and selectivity of isomerization depend on the sequence of addition of salts and reagent to the catalytic system. The simultaneous addition of ZnCl₂ or AlCl₃ with olefin, produces a 2–3 fold increase in the isomer yield compared to ethanol.

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Pd/Al₂O₃- (5 .% Pd) -1, , -, 4--2- (). , . ZnCl₂ AlCl₃ 2–3 .

     

New instruments and methods for enthalpimetric analysis and calibration

A review is given of recently developed instruments used in thermometric analysis and new methods of direct injection enthalpimetry.In the past two years, several types of Tronac (Orem, Utah) and Setaram (Lyon, France) calorimeters have been developed. A new mixing cell construction led to development of a flow instrument for automated thermometric analyses (Technicon, Tarrytown N. Y.). A new type of Hungarian instrument, Ditermanal (Orion, Budapest) permits arbitrary analyses.At the Technical University in Brno, small table twin isoperibol instruments allowing the direct analyses of solid samples have been developed. The use of PTC thermistors and a calibration device improved the accuracy of measurements.Many new methods of silicate and lime analysis, water determination, etc. have been elaborated.

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Zusammenfassung Eine Übersicht über die zur thermometrischen Analyse eingesetzten, entwickelten Instrumente und neuen Methoden der Direkt-Injektion Enthalpimetrie wird gegeben.In den zwei vergangenen Jahren wurden verschiedene Kalorimetertypen TRONAC (Orem, Utah) und SETARAM (Lyon, France) entwickelt. Eine neue Mischzellenkonstruktion ermöglichte es ein Durchflussinstrument für automatische thermometrische Analysen (TECHNICON, Tarrytown, N. Y.) zu entwickeln. Ein neuer ungarischer Instrumententyp, DITERMANAL (ORION, Budapest), ermöglicht die Durchführung von Schiedsanalysen.An der Technischen Universität Brno wurden kleinen Zwillings-Isoperibol-Tisch Instrumente entwickelt, welche auch die direkten Analysen fester Proben ermöglichen. Der Einsatz von PTC-Thermistoren und einer Eichvorrichtung erhöhte die Messgenauigkeit.Viele neue Methoden der Silikat- und Kalkanalyse, Wasserbestimmungen usw. wurden erarbeitet.

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Résumé On passe en revue les instruments récemment mis au point et utilisés en analyse thermométrique ainsi que les nouvelles méthodes d'enthalpimétrie par injection directe.Dans les deux dernières années, divers types de calorimètres ont été mis au point: TRONAC (Orem, Utah) et SETARAM (Lyon, France). La réalisation d'une nouvelle cellule de mélange a permis de mettre au point un appareil à flux pour les analyses thermométriques automatiques (TECHNICON, Tarrytown, N. Y.). Un nouveau type d'instrument hongrois, DITERMANAL (ORION, Budapest) permet d'effectuer des analyses arbitrales.A l'université technique de Brno de petites tables instruments jumeaux isopériboliques permettant aussi d'effectuer des analyses directes des corps solides ont été réalisés. L'application de thermistors PTC et un dispositif pour l'étalonnage augmentent l'exactitude des mesures.Des méthodes nouvelles nombreuses pour l'analyse des silicates, des pierres calcaires, de l'eau, etc., ont fait l'objet d'études.

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, . (, ) (, ). (H, , -). (, ) . , . . , , .

     

Studies of the structure of multicomponent Raney nickel catalysts

Genesis and structure of Raney nickel catalysts modified by Mo, Fe and Ca have been studied by XPS, SIMS and Auger and electron microprobe methods. It has been established that these catalysts are inhomogeneous and their structure can be described by models accounting for the interaction and localization character of metal components, their oxides and hydroxides.

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, - Ni-, Mo, Fe Ca. , , , .

     

Thermal analysis study of the dynamic decomposition of polymers during rapid heating; limiting temperatures of thermolysis

A new technique is presented for study of the thermal behaviour of materials. Experimental and theoretical bases are established for the limiting temperatures of thermal decomposition of different polymers.

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Zusammenfassung Es wird ein neues Verfahren zur Untersuchung des thermischen Verhaltens von Stoffen. vorgestellt. Es wurden experimentelle und theoretische Grundlagen zur Bestimmung von thermischen Zersetzungstemperaturen verschiedener Polymere erstellt.

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. .

     

Measurement of the rate constant of hydrogen atoms with carbon monoxide in tubular and jet stirred open reactors

The reaction of hydrogen atoms with carbon monoxide has been studied in discharge flow systems with a new method of detection of atoms. The results obtained with tubular and jet stirred open reactors agree with those of other authors working in transient conditions and with more sophisticated techniques.

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. , , , .